• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.87.2-87.2
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• 2017

RR~Telescopii is a symbiotic nova exhibiting accretion activities through gravitational capture of the slow stellar wind from a Mira variable. We present high resolution spectra of RR~Tel obtained with MIKE and the 6.5 m Magellan-Clay telescope, in which we find broad features with FWHM exceeding $10{\AA}$ at 6545, 6825, 7082, 7023 and $7053{\AA}$. They are formed through Raman-scattering with atomic hydrogen of far-UV He II 1025, O~VI 1032, $1038{\AA}$ and C II 1036 and $1037{\AA}$. We compute the Raman conversion efficiencies using the case B recombination theory for He II emissions, which are used in turn to infer the intrinsic line luminosities of O VI and C II. The Raman O~VI features are characterized by double-peaked profiles with a peak separation ~ 60km/s, pointing out the presence of an accretion disk with a physical size of ~ sub AU. In contrast, Raman C II features exhibit profiles with a simple peak and a narrower width ~40 km/s, indicating that C II is formed in a much more extended region. The weak C II multiplet at 1335, $1336{\AA}$ found in the IUE spectral archive and the absence of C II 1036, $1037{\AA}$ in the FUSE archive show that far-UV C II lines suffer heavy interstellar extinction consistent with the distance of ~ 2.5 kpc to RR Tel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.37-46
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• 2017

Thermal Marangoni flow has been observed inside droplets on heated surfaces, finally resulting in a coffee stain effect. This study aims to visualize and control the thermal Marangoni flow by employing periodic vertical vibration. The variations in the contact angle and internal volume of the droplet as it evaporates is observed by using a combination of continuous light and a still camera. With regard to the internal velocity, the particle image velocimetry system is applied to visualize the internal thermal Marangoni flow. In order to estimate the internal temperature gradient and surface tension on the surface of a droplet, the theoretical model based on the conduction and convection theory of heat transfer is applied. Thus, the internal velocity increases with an increase in plate temperature. The flow directions of the Marangoni and gravitational flows are opposite, and hence, it may be possible to control the coffee stain effect.

• Animal cells and systems
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• v.2 no.4
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• pp.477-481
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• 1998

Previous studies have postulated that isometric animals exert similar locomotory capacity (speed, distance) because the amount of energy available for the motion would be the same regardless of body mass (m). To test propriety of this theory, we examined body shape and take-off potential of two frog species, Rana nigromaculata (powerful jumpers) and Bombina orientalis (slow hoppers). Morphological measurements included thigh muscle mass (indicative of total muscle force), hindlimb length (L, determining acceleration distance), and interilial width (shaping take-off motion). To gauge locomotory capacity, take-off speed (v) and take-off angle ($\theta$) were measured from video analyses, and jump distance (R) and take-off Power ($P_{t}$ ) were calculated from equations $R=V^{2}sin2\theta/g$ and ($P_{t}$＝$㎷^{3}/2L$(where g is the gravitational constant). Scaling exponents of morphometric variables for both species were 0.96-1.11 for thigh muscle mass, 0.28-0.29 for hindlimb length, and 0.30-0.36 for interilial width. Scaling exponents of locomotory performance for the two species were -0.01-0.14 for take-off speed, 0.24-0.31 for jump distance, and 0.66-0.84 for take-off power. The results demonstrate that the frogs of this study showed isometric body shape within species, but that take-off response changed allometrically with body mass, indicating that these data did not fully support the previous proposition. An exception was found in take-off speed of B. orientalis, in which the speed changed little with body mass (slope＝-0.01). These findings suggest that the energy availability approach did not properly explain the apparent allometric relations of the take-off response in these animals and that an alternative model such as a power production approach may be worth addressing.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.57-62
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• 1990

This paper deals with the flow caused by a two-dimensional pulsating source, which moves with a constant horizontal speed beneath the free surface. The analysis is based on lincar potential theory including surface tension effects. In the case of subcritical reduced frequencies $\tau<1/4(\tau=U_{\omega}/g$, U=constant speed, $\omega$=circular frequency, g=gravitational acceleration), six wave components arc found. Two of them are largely affected by surface tension, which propagate ahead of the source in the direction of and opposite to the steady translation, respectively. The rest are almost identical with those found by Haskind(1954), i.e. for which the surface tension effect is negligible. For low oscillation frequencies, the resonant frequency still exists at $\tau$ only slightly greater than 1/4. For oscillation frequencies greater than $\nu(={\omega}^2/g)>20$, the surface tension effect is so significant that it disperses generated waves and consequently the singular phenomenon is removed. However, in addition to the gravity breaking, capillary breakings occur when the translation speed coincides with the minimum capillary celerity.

• Journal of the Korean Geotechnical Society
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• v.26 no.6
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• pp.5-19
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• 2010

The purpose of this study is to figure out the effect of pressurized grouting on the pullout resistance and the group effect of the compression ground anchor by performing pilot-scale chamber tests and field tests. The laboratory tests are carried out for 3-types of soils which are abundant in the Korean peninsular. Experimental results showed that the enlargement of anchor diameters estimated from the cavity expansion theory matches reasonable well with that obtained from experiments. Moreover, the required injection time as a function of the coefficient of permeability of each soil type was proposed. A series of in-situ anchor pullout tests were also performed to experimentally figure out the effect of pressurized grouting on the pullout resistance. Experimental results also showed that the effect of the pressurized grouting is more prominent in a softer ground with smaller SPT-N value in all of the following three aspects: increase in anchor diameter; pullout resistance; and surface roughness. The pressurized grouting effect in comparison with gravitational grouting was found to be almost nil if the SPT-N value is more than 50. Based on experimental results, a new equation to estimate the pullout resistance as a function of the SPT-N value was proposed. And based on in-situ group anchor pullout tests results, a new group effect equation was proposed which might be applicable to decomposed residual soils which are abundant in the Korean peninsular.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.305-317
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• 2005

This study addresses the preliminary results of rock slope stability analyses including hazard assessments for slope failure conducted on the selected sections of rural road cut slope which are about 4 km long. The study area is located in the Mt. Chuntae northeast of Busan and mainly composed of Cretaceous rhyolitic ash-flow tuff', fallout tuff, rhyolitc and andesite. The volcanic rock mass in the area has a number of discontinuities that produce a potentially unstable slope, as the present cut slope is more than 70 degrees in most of the slope sections. Discontinuity geometry data were collected at selected 8 scanline sections and analyzed to estimate important discontinuity geometry parameters to perform rock slope kinematic and block theory analyses. Kinematic analysis for plane sliding has resulted in maximum safe slope angles greater than $65^{\circ}$ for most of the discontinuities. For most of the wedges, maximum safe cut slope angles greater than $45^{\circ}$ were obtained. Maximum safe slope angles greater than 80" were obtained fur most of the discontinuities in the toppling case. The block theory analysis resulted in the identification of potential key blocks (type II) in the SL4, SL5, SL6 and SL8 sections. The chance of sliding taking place through a type ll block under a combined gravitational and external loading is quite high in the investigated area. The results support in-field observations of a potentially unstable slope that could become hazardous under external forces. The results obtained through limit equilibrium slope stability analyses show how a stable slope can become an unstable slope as the water pressure acting on joints increases and how a stable slope under Barton's shear strength criterion can fail as the worst case scenario of using Mohr-Coulomb criterion.

• Analytical Science and Technology
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• v.27 no.1
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• pp.34-40
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• 2014

SPLITT fractionation (SF) allows continuous (and thus a preparative scale) separation of micronsized particles into two size fractions ('fraction-a' and 'fraction-b'). SF is usually carried out in a thin rectangular channel with two inlets and two outlets, which is equipped with flow stream splitters at the inlet and the outlet of the channel, respectively. A new large scale splitter-less gravitational SF (GSF) system had been assembled, which was designed to eliminate the flow stream splitters and thus is operated by the full feed depletion (FFD) mode (FFD-GSF). In the FFD mode, there is only one inlet through which the sample is fed. There is no carrier liquid fed into the channel, and thus prevents the sample dilution. The effects of the sample-feeding flow rate, the channel thickness on the fractionation efficiency (FE, number % of particles that have the size predicted by theory) of FFD-GSF was investigated using industrial polyurethane (PU) latex beads. The carrier liquid was water containing 0.1% FL-70 (particle dispersing agent) and 0.02% sodium azide (used as bactericide). The sample loading rate was varied from about 4 to 7 L/hr with the sample concentration fixed at 0.01%. The GSF channel thickness was varied from 900 to $1300{\mu}m$. Particles exiting the GSF channel were collected and monitored by optical microscopy (OM). Sample recovery was monitored by collecting the fractionated particles on a $0.45{\mu}m$ membrane filter. It was found that FE of fraction-a was increased as the channel thickness increases, and FE of fraction-b was increased as the flow rate was increased. In all cases, the sample recovery has higher than 95%. It seems the new splitter-less FFD GSF system could become a useful tool for large scale separations of various types of micron-sized particles.